In the cleaning technology for electronic materials represented by a magnetic disk substrate, flat panel display substrate, semiconductor substrate, and the like, control of the cleaning step has become very important because, with progress in the microfabrication technology typified by VLSI and the like, trace amounts of impurities and organic matter remaining on the electronic materials, especially substrates, have great influence on the performance and yield of the devices. In particular, the particles themselves, which are the target of the cleaning, tend to become fine-grained in recent years and the fine-grained particles become more liable to adhere to the interface. Therefore, establishment of an advanced cleaning technology has become a matter of urgent need.
In order to prevent contamination by these particles, there have been proposed methods such as lowering zeta potential on the particle surface by addition of surfactants and thereby reducing the particle adhesion (refer to PTLs 1 to 3).